It is well known that the hardened cementitious material such as cement paste, mortar, concrete etc, is gradually deteriorated in the natural environment from the surface thereof. When such contains steel materials, there is caused rust in said materials as said deterioration progresses so as to generate cracks in the hardened material. In the cementitious material in which the aggregate to cause alkali-aggregate reaction is arranged, the material is swelled as the reaction progresses so as to generate cracks.
As a method for preventing such hardened cementitious material and repairing such deteriorated material, Japanese KOKOKU Gazette Sho 42(1967)-22957 (laid open for public inspection) discloses cement composition added with calcium nitrite. Japanese KOKOKU Gazette Sho 57(1982)-11988 proposes a process comprising steps of coating the surface of the deteriorated cementitious material with aqueous solution of a silicate and then with cement paste which may contain a rust inhibitor.
Japanese KOKAI Gazette Sho 61(1986)-256951 (laid early open) discloses combining of lithium nitrite in cementitious material comprising the aggregate which is to cause alkali-aggregate reaction. In KOKAI Gazette Sho 62(1987)-265189, there is described a method of covering the concrete surface with a sheet or a mat impregnated with aqueous solution of a nitrite.
According to the method of said KOKOKU Gazette Sho 42-22957 in which calcium nitrite is added to the cement composition, however, when the amount of calcium nitrite added in usual Portland cement is increased up to about 5 weight % in relation to cement content, unusual setting directly after kneading or excessive shortening of setting time which adversely affects on the workability of the concrete.
According to the method of said KOKOKU Gazette Sho 57-11988 where aqueous solution of a silicate is applied on the concrete surface, the rust inhibitor in the cement paste then applied can not penetrate into the inner portion. It is silent of what sort of rust inhibitor is to be used.
Said KOKAI Gazette Sho 61-256951 is silent of how aqueous solution of lithium nitrite penetrates the hardened concrete from the surface. According to the usual applying method, such solution cannot penetrate into the inner portion of the concrete.
It is possible to make aqueous solution of lithium nitrite to penetrate into the inner portion according to the method disclosed in said KOKAI Gazette Sho 62-265189, but it is inadvantageous that troublesome after treatments such as filling up of broken off portions and covering up the surface with cement paste, cement mortar etc. are necessary.
Thus, an object of the invention or technical problem to be dissolved in this field is to provide a method for applying a treatment agent so as to penetrate into the inner portion of the hardened cementitious material and so as to prevent the steel materials embedded in said cementitious material from being corroded and hinder the alkali-aggregate reaction, without necessity of troublesome after treatments.
The other advantages will be appreciated by reading the following explanations to be made in further detail.